(i) Field of the Invention
This invention relates to a pipe cutting device, particularly, but not exclusively for cutting plastics pipes.
(II) Prior Art
Well-known pipe cutting devices are, generally, of heavy construction and are provided with means for maintaining substantial radially inwardly directed forces against a cutting wheel which is pressed into and then moved about the periphery of the pipe to effect cutting. Typically, such devices may include a pair of jaws slidable or pivoted for movement towards and away from each other and one of which carries the cutting wheel. The jaws are, for example, movable towards and away from each other by rotating a screw threaded shank passing through a threaded aperture in one jaw and pressing against the other jaw, the shank usually extending outwardly to provide a lever of some length. With such an arrangement, the necessary force for engaging the cutting wheel with the pipe periphery can easily be generated by screwing the threaded shank to press the movable jaw firmly against the pipe, whilst the long lever arm provided by the shank provides for force multiplication to enable a user to generate a force sufficient to turn the pipe cutter around the periphery of the pipe, this force being not insignificant because the friction forces between the cutting wheel and pipe are high in consequence of the high radial force applied to the wheel.
Devices for cutting plastic pipes have tended to follow the pattern of devices previously developed for cutting metal pipes, with only relatively small modifications. Particularly, devices for cutting plastics pipes normally include some mechanical means such as the aforementioned screw threaded shank which can be operated to apply a constant and substantial force to press a cutting wheel against the periphery of the pipe. Now, the operation of positioning a cutting device of this type on a pipe, for use of the device, is somewhat inconvenient since the user must hold the device in one hand and screw the threaded shank with the other so that the jaws exert pressure against the pipe. Thus, the pipe must normally be mechanically held during fitting of the device to the pipe, because the user has no free hand to use for this purpose. It is one object of the invention to provide a pipe cutting device for plastic pipes which is more convenient in use.